I am missing some concept with linux disk management, I have free space on a single physical volume that I want to to extend an ext4 file-system with, which is a logical volume.
I look at fdisk -l - it is a GPT (warnings)
Disk /dev/sda: 299.4 GB, 299439751168 bytes
255 heads, 63 sectors/track, 36404 cylinders, total 584843264 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sda1 1 584843263 292421631+ ee GPT
I look at the physical volumes:
root@node-29:/home# pvs
PV VG Fmt Attr PSize PFree
/dev/sda4 os lvm2 a-- 62.00g 4.00m
/dev/sda5 logs lvm2 a-- 10.00g 4.00m
/dev/sda6 mysql lvm2 a-- 20.00g 4.00m
/dev/sda7 narcine lvm2 a-- 11.00g 4.00m
this adds up to 93GB, the is a swap partition and a few others but, I have lots of free space
I look at parted, since they are GPT partitions - I want to see the free space available:
root@node-29:/home# parted /dev/sda print free
Model: DELL PERC H710 (scsi)
Disk /dev/sda: 299GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
17.4kB 1049kB 1031kB Free Space
1 1049kB 26.2MB 25.2MB primary bios_grub
26.2MB 27.3MB 1049kB Free Space
2 27.3MB 237MB 210MB primary
237MB 238MB 1049kB Free Space
3 238MB 448MB 210MB ext2 primary
448MB 449MB 1049kB Free Space
4 449MB 67.1GB 66.6GB primary
67.1GB 67.1GB 1049kB Free Space
5 67.1GB 77.9GB 10.8GB primary
77.9GB 77.9GB 1049kB Free Space
6 77.9GB 99.4GB 21.5GB primary
99.4GB 99.4GB 1049kB Free Space
7 99.4GB 111GB 11.9GB primary
111GB 111GB 1049kB Free Space
8 111GB 111GB 21.0MB ext2 primary
111GB 299GB 188GB Free Space
there's a little free space on all the volumes but there is the space I want on the last line
Number Start End Size File system Name Flags
111GB 299GB 188GB Free Space
In LVM I see the devices are in /dev/mapper, I look at dmsetup
root@node-29:/home# dmsetup info
Name: narcine-nartemp
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 252, 0
Number of targets: 1
UUID: LVM-eDmr02vsptbjvAdvX9c7VZGuI3drAkuMqYAIwCAy6EEZ2GTAopLlD96o6CmOtszP
Name: os-swap
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 2
Event number: 0
Major, minor: 252, 4
Number of targets: 1
UUID: LVM-hMIdqpNc1W6paxT044lNpBcPUfWGA2kESL4f6dB9OJu14mKzLvnOzKMeNM6zV4SK
Name: os-root
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 252, 3
Number of targets: 1
UUID: LVM-hMIdqpNc1W6paxT044lNpBcPUfWGA2kEcIBDlsTce6uqieEfh6ehzYfLxJwaIoEe
Name: mysql-root
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 252, 1
Number of targets: 1
UUID: LVM-rYCHA1YXEPa6jDTS8NIHRvTXllf7jeNhT5d7pulT4efAq4TMll6ndWVuyiDYgGbs
Name: logs-log
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 252, 2
Number of targets: 1
UUID: LVM-npxUm7C9dQX7fIrLeAGyfJxrDWKzmb9rVfJS8FEspobIPK8bnuOnDzLNdQtsY4jE
how should I proceed with extending? what is the order (parted, lvm, dmsetup?) - parted tells me the device partition is loop - what does that mean?
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/os-root: 53.7GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Number Start End Size File system Flags
1 0.00B 53.7GB 53.7GB ext4
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/os-swap: 12.9GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Number Start End Size File system Flags
1 0.00B 12.9GB 12.9GB linux-swap(v1)
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/logs-log: 10.7GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Number Start End Size File system Flags
1 0.00B 10.7GB 10.7GB ext4
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/mysql-root: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Number Start End Size File system Flags
1 0.00B 21.5GB 21.5GB ext4
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/narcine-nartmp: 11.8GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Number Start End Size File system Flags
1 0.00B 11.8GB 11.8GB xfs
I expected pvsan -vv to show me free PEfree on /dev/sda - why doesn't it?
what's throwing me is the command dmcreate it looks like with this, there is no need to create "traditional" partitions - is that correct?
thanks.
How to extend the LVM
Explanation of LVM
LVM doesn't care about partitions. A LVM has the following hierachy:
Lets go from the bottom up.
At the bottom you have the hardware. Big surprise. On top of that you have PVs. Now here is where it becomes confusing. You can either have a PV be the drive itself or a partition. LVM does not need partitions. You can add raw block devices as PVs. However, many people create partitions anyways. There are many reasons for this. Backwards compatibility with tools or people that expect partitions, for example. If a sysadmin does not know the layout and sees an 'empty' disk, he might think the disk is empty, although it is a PV! So thats the reason why you sometimes use partitions as PVs.
This is what you see in your example, whoever set the server up created one partition per VG, apparently.
Next up are the volume groups. A VG is one or multiple PVs. This is the container that holds all the stuff that comes afterwards. Since PVs can be disks, virtual disks from RAID controllers, partitions, etc., VGs can span any number of these things.
On top of VGs you have LVs. This is what you actually put your filesystems on top of. You can look at a LV kind of like a partition. You can find them here:
So a LV always belongs to one VG, but you can have many LVs per VG.
On top of the LV, finally, you put your filesystem.
Why loop
The loop conundrum: there is no loop device! Parted cannot find a partition table on the LVM (as it should be), so it just displays 'loop' instead.